Electrical interlock circuit



United States Patent The invention hereinafter described and claimed has to do with electrical circuits, but more specifically to elec trical interlock circuits for controlling a plurality of operative devices whereby selective operation of said devices may be ellected and in a manner making it impossible to operate more than one at a time.

The primary object of the invention is to provide an electrical circuit such as indicated above, and which is characterized by its simplicity, its reliability, and its eco nomical construction.

In accordance with the above, and first briefly described, the invention comprises circuit means for controlling a plurality of operative devices and having interlock means whereby only one of said devices may be operated at a time, and means for automatically resetting for another operation.

The various features and details or" the circuit of the present invention are hereinafter more fully set forth with reference to the accompanying schematic drawing illustrating the preferred embodiment thereof.

With reference to the drawing it is seen that the circuit may best be described by dividing it into four component circuits, the first of which comprises a plurality of switches lll, only three of which, llt 16A and MB, are shown, and preferably of the single pole, double throw variety, connected in series across a power line 11 having lines A and B for supplying suitable voltage, and in series with a switch 12, contact K3l of switch 13, and the coil of a relay K1. Each of the switches It) is operatively and respectively associated with a solenoid 14, 14A and 143, connected in parallel in the second component circuit and to power line B.

The solenoids are operatively connected by their armatures IE, ISA and 1513 respectively, to devices 16, 16A and 16B, each to be operated upon energization of its associated solenoid. These devices may be any number of different types, or if desired, may be article ejection apparatus such as described in the co-pending application entitled Article Storing and issuing Apparatus, Serial No. 187,636, filed April 16, 1962, in the name of Richard I. Kester, and assigned to the assignee of the subject invention.

Relay K1 includes the normally closed switch 13 in the third of the component circuits, identified by the reference character 20 (at the bottom of the drawing), which also has a relay coil K2 and a start switch 22, all connected in series across a suitable source of voltage indicated at 24. It should be understood that switch 22 in the present illustrated embodiment of the invention is disposed in a position which is inaccessible until switch 12 is closed, as more clearly set forth in the Brewer et al. application identified below. The switch 25 of relay K2 is connected in a DC. circuit 25, the fourth component circuit, having in series, relay contact KZ-ll, relay coil K3 and a capacitor 28. Connected in shunt to contact 312-2 of switch and the line 29 between capacitor 23 and the minus side of; the circuit, is a resistor 3d.

In the operation of the circuit to energize or operate one of the output devices 16, MA or 158, one or" the single pole, double throw switches ltl is moved from its No. 1 to its No. 2 contact, either manually, or in the manner set forth in the co-pending application entitled inventory Control System and Apparatus, Serial No. 162,630, filed December 12, 1961, in the names of Brewer, White and 3,160,793 Patented Dec. 8, 1964 Colburn, and assigned to the assignee of the present in vention. Reference may be had to that application for further details, if desired, although it is not necessary to a complete understanding of the present invention. It is only necessary to know here, that actuation of one of the switches by any means, selects the particular device to be operated.

Normally the circuit is connected to the power source 11 as by closing switch 12, which may be manually operated, or it may be closed by the opening of a door as set forth in the above mentioned Brewer et a1. application, or by some other means, not shown. Closing of switch 12 completes a chcuit from one side A of the line through the switch, and then successively through the series-connected switches lib, MA and NB, contact K34 of switch 13, the coil of relay K1 to the other side B thereof, thus energizing relay R1 to move its switch 18 to open condition against contact Kit-l, as illustrated by the broken line. T he circuit is now in its ready condition for selective operation or" one of the devices 16, 16A or 16B.

Let it be assumed, for purposes of illustration, that it is desired to operate the No. 2 device 16A, in which case the pole of switch lldA is moved from its No. 1 contact, shown in full line, to its No. 2 contact, as shown by the broken line. This opens the circuit through relay K1, dropping it out and returning its associated switch arm (switch 18) from contact Ell-1 to contact (1-2, as shown by the full line, thus readying the circuit for energization by closure of start switch 22;. It is understood, of course, that switch 13 is still in its full line condition (on contact (3-1) and that no power is being fed to the solenoid 14A as yet. Depression of start button 22 will now energize relay K2 to move switch 25 from its KZ-Z contact to its K2-1 contact causing the coil of relay K3 to be momentarily energized by displacement current through capacitor 28.

'Relay K3 will move its switch 13 from contact (3-1 in line B to contact Kit-2 in line A closing the circuit from line A through contact No. 2 of switch 10A and solenoid coil MA to line B, thus to eiiect operation of the device 16A through armature 15A. The surge of dis placement current through DC. circuit 26 will continue until the capacitor 25; charges, approximately .25 second with the values set forth below by way of example. During' the initial surge, the coil 14A is energized, as described above, but when the capacitor reaches full charge, power to relay K3 cuts oil and it will drop out, moving its switch it? bacl: to the full line condition (K3-1 contact) opening the circuit to relay 14A.

in particular accordance with the present invention, it will be understood that only one of switches 10, 10A or Mill can be operative at one time, thus interlocking the circuit by locking out operation of more than one of the devices if, for example, more than one switch is moved to its operative condition (on No. 2 contact), as shown in the drawing, it can be seen that electrical energy can flow only through the switch 10 closest to line switch 13. if switch 1GB is on its No. 2 contact, current cannot flow through this swit h to switch WA, or any of the others to the left of switch MB.

Thus, it is obvious that only one of the devices 10 can be operated at a time and that a second article cannot be issued until completion of a cycle of operation and re setting of the circuit, as described below.

Referring to DC. circuit 26, it will be understood when capacitor 23 is fully charged that current to relay K3 is cut oil causing it to drop out, and if at this time the start button has been released (opened) the circuit will reset to its normal condition ready for selection of another, or even the same switch Ill.

In the drawing, it wil be noted that the operative devices 16 are numbered No.' l, No. 2 and No. X to indicate that any number of devices may be connected in the series,-

the circuit lines being indicated as broken between switches and 10A for this purpose.

The resistor 30, in shunt around relay coil K3 and capacitor 28, from switch 25 to the negative side of the line in circuit 26, is effective when the switch is in the full line condition shown, to discharge the capacitor 28 to ready the circuit for a subsequent operation. From the above, it is seen that start button 22 must be released before a second selection can be made, thus effecting a built-in reset feature in the circuit.

By way of example, the relay K3 may have a value of 10,000 ohms, the resistor a similar value, the capacitor a value of 12 t, and all of the circuits may be supplied with 115 volts.

From the above, it is now clear that the invention provides an electric circuit having all of the characteristics and advantages set forth above.

What is claimed is:

1. Electrical circuit means for selectively effecting operation of only one of a plurality of devices, comprising:

(A) first and second component circuits each connectible to a source of voltage;

(B) said second circuit having a plurality of electrically responsive means, each for actuating only one of said devices when energized;

(C) said first and second circuits having series connected first and second switch means in common and in normally closed condition in said first circuit and normally open condition in said second circuit;

(D) said first switch means comprising a plurality of switches each operable to connect only one of said electrically responsive means in said second circuit;

(E) electrically operative means for actuating said second switch means from its normally closed condition in said first circuit to close its normally open condition in said second circuit thus cooperating with said first switch means to connect said second circuit to its voltage source to energize the selected one of said electrically responsive means thus to effect operation of the device selected by said first switch means;

(F) and means in said first circuit rendering said electrically operative means inoperative while said first and second switch means are connected in series circuit in said first circuit but to render it operative upon the closure of one of said plurality of switches in said second circuit.

2. Electrical circuit means for selectively effecting oceration of only one of a plurality of devices, comprising:

(A) first and second component circuits each connectible to a source of voltage;

(B) said second circuit having a plurality of electrically responsive means, each for actuating only one of said devices when energized;

(C) said first and second circuits having series connected first and second switch means in common and in normally closed condition in said first circuit, and normally open condition in said second circuit;

(D) said first switch means comprising a plurality of switches each operable to connect only one of said electrically responsive means in said second circuit;

(E) additional normally open circuit means for actuating said second switch means from its normally closed condition in said first circuit to close its normally open condition in said second circuit thus cooperating with said first switch means to connect said second circuit means to its voltage source to energize the selected one of said electrically responsive means thus to effect operation of the device selected by said first switch means;

(F) means in said first circuit in response to movement of the said one of said plurality of switches of said first switch means to connect one of said electrically responsive means in said second circuit to render said additional circuit means in condition for actuation of'said second switch means; and

(G) means for connecting said additional circuit means with a voltage source thus to effect actuation of said second switch means to connect said second circuit to its voltage source and effect operation of the selected device by energization of the selected electrically responsive means.

3. Circuit means according to claim 2 wherein said additional circuit means comprises:

(A) third and fourth normally open component cir cuits;

(B) means in said first circuit for controlling said third circuit for closure with a voltage source;

(C) means in said third circuit for closing said fourth circuit with a voltage source; and

(D) means in said fourth circuit for so moving said second switch means from its closed condition in said first circuit to close said second circuit with said voltage source thus to efiect the said operation of the selected device.

4. Circuit means in accordance with claim 3 and further comprising:

(A) means in said fourth circuit automatically to cut it oil from its voltage source after only momentary energization thereof in a manner effecting an auto matic resetting of said circuit means upon re-opening of said third circuit.

5. Circuit means according to claim 4 wherein:

(A) said automatic cut-oil means comprises a capacitor in series circuit with said means in said fourth circuit for moving said second switch means; and

(B) said reset means comprises a resistor in shunt around said last mentioned means and said capacitor whereby said capacitor is discharged upon open ing of said third circuit.

6. An electrical circuit for operating selected ones of a plurality of operative devices, comprising:

(A) solenoid means operatively associated with each of said devices;

(B) a first switch operatively associated with each of said solenoids,

(1) each of said first switches being of the single pole, double throw type with their normally closed contacts connected in series, and the normally open contact of each connected to one of said solenoids, and

(2) said solenoids being connected in parallel to one side of a source of voltage;

(C) means to connect said series connected contacts of the switches to a source of voltage, said connecting means comprising,

(1) the normally closed side of a second single pole, double throw switch, and

(2) a first relay coil,

(3) the normally open side of said second single pole, double throw switch being connected to a source of voltage;

(D) a start circuit comprising in series,

(1) first and second switches, and

(2) a second relay coil;

(E) a DC. circuit having connected in series,

(1) a third single pole, double throw switch,

(2) a third relay coil, and

(3) a capacitor; and

(F) a resistor in said D.C. circuit connected in shunt across said circuit around said third relay coil and said capacitor,

(G) the movement of one of said first switch means to connect one of said solenoid means for operation of a selected device being efiective to de-energize the said first relay coil which de-energization is eliective to close the said second switch in said start circuit;

(H) closure of said first switch after the closure of said second switch in said start circuit being effective to energize said second relay to move the switch in said D.C. circuit in position to connect the circuit to its source of voltage thereby energizing said third relay; and

(I) said third relay being effective to move said second single pole, double throw switch to its normally open side, thus to connect said electrically responsive means to its source of voltage to cause actuation of the selected device.

7. An electrical circuit for operating selected ones of a plurality of operative devices, comprising:

(A) individual solenoid means operatively connected by armature to each of said devices;

(B) a plurality of first switches each operatively associated with only one of said solenoids,

(1) each of said first switches being of the single pole, double throw type with their normally closed contacts connected in series and the normally open contact of each connected to a different one of said solenoids,

(2) said solenoids being connected in parallel to one side of a source of voltage;

(C) means to connect said series connected contacts of the switches to first and second lines of a source of voltage, said connecting means comprising,

(1) the normally closed side of a second single pole, double throw switch, and i (2) a first relay coil connected to said second line,

(3) the normally open side of said second single pole, double throw switch being connected to a source of voltage having the same polarity as said first line;

(D) a start circuit comprising in series,

( 1) first and second single pole, single throw switches, and

(2) a second relay coil; and

(E) a DC. circuit having connected in series,

(1) a third single pole, double throw switch,

(2) a third relay coil,

(3) a capacitor; and

(4) a resistor connected in shunt across said cir- 6 cuit around said relay coil and said capacitor;

(F) said first relay coil being operatively connected to said second switch in said start circuit;

(G) said second relay coil being operatively connected to said third single pole, double throw switch in said D.C. circuit; and

(H) said third relay coil being operatively connected to said second single pole, double throw switch; whereby (I) the movement of one of said first switches to connect one of said solenoids for operation of a selected device being effective to deenergize the said first relay coil which is eifective to close the said second switch in said start circuit;

(J) closure of said first switch in said start circuit after the closure of said second switch being effective to energize said second relay coil to move the single pole, double throw switch in said D.C. circuit in position to connect the circuit to its source of voltage thereby energizing said third relay coil;

(K) said third relay coil being eliective to move said second single pole, double throw switch to close its normally open side with said first line, thus to connect said electrically responsive means to its source of voltage to actuate the selected device;

(L) said capacitor providing means for cutting off voltage to said third relay coil after only momentary energization of the coil; and

(M) said resistor providing means to de-energize said capacitor after re-opening of said start circuit.

References Cited by the Examiner UNITED STATES PATENTS 1/59 Wiswell 307-141 2/61 Ebert 317-137 

1. ELECTRICAL CIRCUIT MEANS FOR SELECTIVELY EFFECTING OPERATION OF ONLY ONE OF A PLURALITY OF DEVICES, COMPRISING: (A) FIRST AND SECOND COMPONENT CIRCUITS EACH CONNECTIBLE TO A SOURCE OF VOLTAGE; (B) SAID SECOND CIRCUIT HAVING A PLURALITY OF ELECTRICALLY RESPONSIVE MEANS, EACH FOR ACTUATING ONLY ONE OF SAID DEVICES WHEN ENERGIZED; (C) SAID FIRST AND SECOND CIRCUITS HAVING SERIES CONNECTED FIRST AND SECOND SWITCH MEANS IN COMMON AND IN NORMALLY CLOSED CONDITION IN SAID FIRST CIRCUIT AND NORMALLY OPEN CONDITION IN SAID SECOND CIRCUIT; (D) SAID FIRST SWITCH MEANS COMPRISING A PLURALITY OF SWITCHES EACH OPERABLE TO CONNECT ONLY ONE OF SAID ELECTRICALLY RESPONSIVE MEANS IN SAID SECOND CIRCUIT; (E) ELECTRICALLY OPERATIVE MEANS FOR ACTUATING SAID SECOND SWITCH MEANS FROM ITS NORMALLY CLOSED CONDITION IN SAID FIRST CIRCUIT TO CLOSE ITS NORMALLY OPEN CONDITION IN SAID SECOND CIRCUIT THUS COOPERATING WITH SAID FIRST SWITCH MEANS TO CONNECT SAID SECOND CIRCUIT TO ITS VOLTAGE SOURCE TO ENERGIZE THE SELECTED ONE OF SAID ELECTRICALLY RESPONSIVE MEANS THUS TO EFFECT OPERATION OF THE DEVICE SELECTED BY SAID FIRST SWITCH MEANS; (F) AND MEANS IN SAID FIRST CIRCUIT RENDERING SAID ELECTRICALLY OPERATIVE MEANS INOPERATIVE WHILE SAID FIRST AND SECOND SWITCH MEANS ARE CONNECTED IN SERIES CIRCUIT IN SAID FIRST CIRCUIT BUT TO RENDER IT OPERATIVE UPON THE CLOSURE OF ONE OF SAID PLURALITY OF SWITCHES IN SAID SECOND CIRCUIT. 